The Internet infrastructure has heretofore been upgraded, and there have been implemented businesses for delivering various contents such as audio data, audio/visual (AV) data, program data, etc. over the Internet.
The types of contract for content delivery over the Internet include a “pay-per-content” contract and “subscription” contract.
Under the “pay-per-content” contract, a specified content or a specified group of contents is sold or bought. Under the “subscription contract”, a right to use a plurality of unspecified contents is sold and bought as is under a monthly contract for a pay channel of television broadcast, for example.
Under any of the pay-per-content and subscription contracts, a content is delivered in an encrypted form and a license including a key for decryption of the encrypted form is also delivered along with the encrypted content.
For example, the Japanese Patent Application Laid Open No. 2002-116856 discloses a method of delivering a license for an encrypted content separately from the encrypted content. Since the license delivery method disclosed in this Japanese Patent Application has to deliver a license for each content, it is suitable for the content delivery under the pay-per-content contract but not for the content delivery under the subscription contract.
A content delivery service under both the pay-per-content and subscription contracts is under development, but a method of delivering a license in that service has not yet been established.